Earth inductor compass indicating system



Feb. 27, 1951 N. MARCHAND 2,543,034

EARTH INDUCTOR COMPASS INDICATING SYSTEM Filed Aug. 21, 1945 @gliPatented Feb. 27, 1951 EARTH INDUCTOR COMPASS INDICATING SYSTEM NathanMarchand, New York, N. Y., assignor to Federal Telephone and RadioCorporation, New York, N. Y., a corporation of Delaware ApplicationAugust 21, 1945, Serial No. 611,889

2 Claims. (Cl. 3 3-204) This invention relates to a compass indicatorand more particularly to an indicator for a compass of the earthinductor type.

Compasses of the type in which a coil is rotated in the earths magneticfield thereby generating a current which may be compared with somestandard for indicating magnetic north are Well known. These compassesare generally termed earth inductor Compasses. Many types of indicatorsystems have been suggested for producing the desired north-southindications. However, in general, such systems fail to provide meanswhereby the sense of the north-south direction may be readily obtainedon an instantaneous type of indicator.

It is an object of my invention to provide an indicating system using arotatableconductive means rotated at a predetermined rate in a magneticeld in which an indicator means is synchronized with the rotation of thepick-up means and the output of the pick-up means is rectied and appliedto an indicator, one portion of the rectified energy being distorted toprovide a sense indication.

It is a further object of my invention to provide an earth inductorcompass including, on a rotatable pick-up coil, a selective lter means,a rectifier means and a cathode ray indicator in which a common drivemeans is provided simultaneously to drive the rotatable coil and thedeiiecting system of the cathode ray indicator.

It is a still further object of my invention to provide in an earthinductor compass as outlined above, means for distorting `or effectivelysup.

pressing certain half cycles of the wave to be rectified so that a Senseof the directional indication may be obtained.

A better understanding of my invention and the objects and featuresthereof may be had from the particular description thereof made withreference to the accompanying drawing, in which:

Fig. 1 is a schematic circuit diagram partly in block illustrating anindicating system in accordance with my invention; and

Fig. 2 is an alternative indicator arrangement which may be used withthe system of Fig. 1.

The earth inductor compass as shown in Fig. 1 comprises essentially arotatable loop or pick-up coil I which may be preferably provided with apermeable iron core. Pick-up coil I is coupled to a selective lter means2 which serves to select only the fundamental Wave produced in therotation of loop I to the exclusion of extraneous elds. The output offilter 2 is coupled over an amplifier 3 and rectier 4 to an indicator 5which may be of the cathode ray type. A motor 6 serves simultaneously todrive coil I and ray deiiecting means I over shafts 8 and 9. The outputfrom rectifier 4 is also supplied to coils 1 producing a directionindicating pattern I0 on the screen I I of indicator 5.

Filter 2 is preferably made extremely selective and as illustrated inFig. 1 mayY comprise a synchronous lilter of the type disclosed morefully in the copending application of G. R. Clark, Serial No. 591,894,led May 4, 1945, which has become abandoned. This filter comprisesessentially a plurality of storage condensers I2 connected on one sideof a plurality of the contact terminals I3 and on the other side to acommon bus I4.` Output leads I5 and I6 from loop I are coupled toterminals I3 and common bus I4 respectively, by brush I'I and lead I8.An output brush I9 serves to take oi energy stored in condensers I2. Therotatable condenser bank and brushes I1 and I9 are rotated relatively toone another at' the same speedas loop I is rotated, for example by shaft20 from motor 6. Since the relative rotation of the condensers I2 issynchronous with rotation of loop I, a charge will tend to build up inthese condensers depending upon the voltage applied thereto from loop I.Because only regularly produced waves will be synchronously repeated,only these regular Waves will cumulatively charge the condensers I2.

The output voltage from the condensers I2 is taken over brush I9 andlead 2| to a coupling tube 22. The output voltage from tube 22 may beapplied over lead 23 to the input of amplilier 3, the cathode lead 24also being coupled to this amplier. The output of amplifier 3 is coupledover transformer 25 to the rectiers 26 and 2l of rectifier means 4. Inthe cathode lines of rectiers 26 and 21 are provided output resistors 28and 29 respectively, which are coupled to coils I of indicator 5. ItWill be evident that a full Wave rectified sine voltage is thus appliedto deection coils l. The indicator 5 preferably has its beam so biasedthat at a zero signal level it will be at the outer edge of the screen.An increase in deecting Voltage in coils I Will tend to deiiect thisbeam toward the center.

If the entire full-Wave rectied voltage were applied, the two lobes 30and 3l of pattern I0 would appear on the screen at equal brilliance andit would not be possible to tell which is north and which is south. Inorder to obtain a sense indication, I provide a trigger circuit 32, asfor example a one shot multivibrator circuit coupled over lead 33 to theoutput of filter 2. This trigger 3 circuit is biased to produce anoutput wave as shown at 34 synchronized with the output wave 35 fromfilter 2 so that negative pulses 36 are produced coinciding withalternate negative half wave cycles of wave 35. The output wave 3d isapplied over 1ead31 tQrectiersJ and 21 serving to block rectificationfor alternateenegative half waves. As a consequence, on the screen ofthe cathode ray tube the pattern 3U which represents the positive halfwave cycles will appear more brilliant than the partoif thepatte 1n 3|which represents the negative half waves.

While in Fig. 1, I have shown an indicator usingA a trigger circuit fordistorting the outputwave by suppression of certain half wave cyclesthereof, a sensing Yindication may be provided simply by distorting theshape of oneofthehalf wave cycles of the output Wave. A circuit foraccom.-l plishing this result is shown in Fig. 2. According toA thisarrangement, output, transformer l25 is C Qupled, to rectifiers 23 and2l" in the same mannerasin Fig. 1`. However, one of the cathoderesistors, f or example cathode resistor 29',Y is shunted by a`condenser 3B. As a consequence, the output pulses for the positive halfcycle will,

be as illustrated at 39. but for the negative half cycle as shown at 4Uthey wi-llI not reduce to Zero. Thus, on indicator 5, a pattern will betraced' having al'obe'ala, representing the direction and asubstantially suppressed` lobe 3 la. representing the other sidev of thearrow. This form of indication may be preferablel to` that shown in Fig.l since, there is nol possibility of error in reading the indication.

While I havedescribed my invention` in accordance with a particularembodiment and particular I rlQdication'thereof;- it should b edistinctly understood that this isA given merely by AWay ofv example;Many Variations in the system inv acthose skilled in the art. It shouldtherefore be clear that the description of the particularY examples ismade merely as illustrative and' not as any limitation on the scope ofmy invention as sof - y 2,489,279 cordance with my invention willreadily occur to 4c f pick-up coil, a rotary condenser filter means, a

two tube, full wave rectiiier means, a cathode ray indicatorhavingrotary deflecting means, means coupling said coil and said rectier meansto said, rotary filter means,common means for simultaneously driving said pick-up coil, rotary lter and deecting means, distorting meansshunting the output of one ofsaid'rectier tubes,

and4 means for applying theoutpu't ofy said rectilier to said'` deectingmeans.

l NATHAN MARCHAND.

REFERENCES CITED The following references are of record in the jiile ofthis patent:

UNITED STATES. PATENTS Number Name,

Date

Stuart Nov. 4, 1941' Busignies et al.y Nov. 18, 1941 FOREIGN PATENTSCountry Date Great Britain May l, 1903 Great Britain July 15, 11937Number Tolson Sept.` 20,133.31

Bonell Apr. 1,0, 1,945v Hardy Apr. 27, 1948 Finzer NOV. 29, 1949.

